The invention pertains to an internal combustion engine with a cylinder head and at least one camshaft supported thereon, which shaft, driven by a crankshaft, actuates corresponding gas-exchange valves on the cylinder head. A camshaft adjuster, which uses hydraulic pressure to rotate the position of the camshaft relative to the crankshaft and thus to change the control times of the gas-exchange valves, is provided on the camshaft. A feed device for supplying hydraulic pressure to the camshaft adjuster is also provided. The invention also pertains to a feed device for supplying hydraulic medium to the camshaft adjuster of a camshaft of an internal combustion engine. The invention also pertains to a process for producing a feed device as indicated above.
A device for changing the control times of the gas-exchange valves of an internal combustion engine is known from DE 197-45,670 A1, where a camshaft adjuster is mounted on one end of a camshaft, which actuates the gas-exchange valves. By means of pressure medium channels provided in a housing cover, the camshaft adjuster is supplied with hydraulic pressure for rotating the position of the camshaft relative to a crankshaft, which drives the camshaft. The housing cover, however, is complicated and expensive to produce and install.
It is known from DE 197-47,244 A1 that ring-shaped grooves can be provided in the cylinder head at one end of a camshaft in the area where the camshaft is supported and that hydraulic medium can be supplied via these ring-shaped grooves to a camshaft adjuster mounted on the camshaft. To prevent losses in the area of the bearing of the camshaft when the hydraulic medium is tapped, a plain bearing ring is laid in a half liner of the bearing, this ring covering the half liner. This integration of the hydraulic medium supply system into the cylinder head itself makes it difficult and expensive to produce the cylinder head. In addition, because the hydraulic medium is supplied by way of the bearing liner of the bearing of the camshaft in the cylinder head, the bearing is weakened to a corresponding extent.
The present invention, therefore, is based on the task of making available an internal combustion engine, a feed device, and a process of the above-indicated type, where the disadvantages described above are overcome, so that an improved and functionally reliable camshaft adjusting function is available.
In an internal combustion engine of the type indicated above, it is provided in accordance with the invention that the feed device for hydraulic pressure is designed as a component separate from the cylinder head and that this device has a ring for each camshaft, each ring surrounding a certain section of the camshaft. Each ring has two grooves, and the associated surrounded section of the camshaft has two ring-shaped grooves, which are aligned with the grooves of the corresponding ring. Each groove/ring-shaped groove pair of a ring is connected via its own set of hydraulic pressure channels in the camshaft to a hydraulic pressure chamber of the camshaft adjuster mounted on this camshaft. Furthermore, each groove/ring-shaped pair of a ring is connected by its own set of hydraulic pressure channels in the feed device to a hydraulic pressure valve.
This has the advantage of making available a system for feeding hydraulic medium to camshaft adjusters which is both simple to produce and simple to install.
In a preferred embodiment, the feed device for hydraulic pressure in the separate component comprises the following integral parts: at least one hydraulic pressure connection, at least one hydraulic tank connection, at least one socket for a hydraulic pressure valve, and corresponding hydraulic pressure channels, which are designed in such a way that they connect each hydraulic pressure connection to a socket which holds a hydraulic pressure valve, each hydraulic pressure valve to a groove/ring-shaped groove pair of a ring, and each socket for a hydraulic pressure valve to a hydraulic tank connection. The socket which holds the hydraulic pressure valve can be, for example, either parallel or perpendicular to the axis of the ring.
Designing the hydraulic pressure valve as a 4/2-port proportional distributing valve makes it possible to provide the camshaft with the capacity to rotate to any desired intermediate position between the two end positions of the camshaft and also to provide it at the same time with a wide rotational range extending over more than, for example, 60xc2x0.
It is advisable to design the feed device in such a way that it can be attached to the cylinder head.
In a feed device of the type indicated above, it is provided according to the invention that this feed device is designed as a component separate from the cylinder head and attachable to it, and that the device has a ring for each camshaft, each ring surrounding a certain section of the camshaft. Each ring has two grooves, which are connected to hydraulic pressure channels in the feed device to a hydraulic pressure valve.
This offers the advantage that, with the use of ring-shaped grooves appropriately provided in the surrounded section of the camshaft and hydraulic pressure channels, a system for supplying hydraulic medium to the camshaft adjuster is provided which is simple both to produce and to install.
In a preferred embodiment, the separate component has the following elements as integral parts: at least one hydraulic pressure connection, at least one hydraulic tank connection, at least one socket for a hydraulic pressure valve, and corresponding hydraulic pressure channels, which are designed in such a way that they connect each hydraulic pressure connection to a socket which holds a hydraulic pressure valve, each hydraulic pressure valve to a groove/ring-shaped groove pair of a ring, and each socket for a hydraulic pressure valve to a hydraulic tank connection. The socket which holds the hydraulic pressure valve can be, for example, either parallel or perpendicular to the axis of the ring.
Designing the hydraulic pressure valve as a 4/2-port proportional distributing valve makes it possible to provide the camshaft with the capacity to rotate to any desired intermediate position between the two end positions of the camshaft and also to provide it at the same time with a wide rotational range extending over, for example, more than 60xc2x0.
To produce the feed device mentioned above, the separate component is, for example, cast as a single piece with the ring or rings and with the socket or sockets for hydraulic pressure valve or valves, and then the hydraulic pressure connection and the hydraulic pressure channels are formed in the separate component by drilling blind holes and through-holes. The ends of the blind holes and through-holes forming the various hydraulic pressure channels which are open toward the outside are then sealed off. The open ends of the through-holes are advisably sealed off by pressing in close-fitting balls, and each hydraulic pressure connection is provided with a nonreturn valve. So that a good seal is provided between the separate component and the cylinder head on which it is mounted, appropriate flange surfaces are produced on the separate component afterwards by grinding, for example, in the areas where the component will rest on the cylinder head.